Version 3 of CMUD requires a new license for all users. As per the CMUD upgrade policy, if you purchased CMUD within the past 2 years, you can get this upgrade for free. But it still requires you to get a new license key.
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To get your new CMUD v3 license key:

Log into your store account with your email and password. If you have forgotten your store password, click the Recover Password link on the main store page and your password will be sent to your email address.

If you no longer have access to the email address you used to register CMUD, you'll need to contact us at support@zuggsoft.com and send us your original license details along with your new email address.

Once you are logged in, simply add the CMUD v3 or CMUDPro v3 product to your shopping cart. The price shown in the cart will reflect any discounts you are eligible for. If you purchased CMUD within the past 2 years, the price should be FREE. Otherwise the price will be listed as half-price. If you never purchased CMUD before, you'll see the full price.

If you have any trouble upgrading your CMUD license, send email to support@zuggsoft.com. We cannot help with license questions on these public forums. The 30-day trial for CMUD has been reset with Version 3, so you should have plenty of time to resolve any upgrade issues before your new trial runs out.

The half-price upgrade offer is good forever, but the price itself might be going up in a few months after the new release promotion is over. If the price of CMUD increases, than obviously the 1/2 price of the upgrade will also go up.